Wide bandgap semiconductor devices, for example based on SiC substrates can provide higher maximal blocking voltages as comparable devices based on Si substrates. The higher maximum blocking voltage in combination with lower switching losses of SiC semiconductor devices allows more flexibility of converter design for medium voltage and high voltage applications.
For example, the entire voltage range of MV applications may be covered with simple two-level voltage source converter topologies. Higher switching frequencies may reduce the total harmonic distortion significantly.
For typical two level or three level topologies in high voltage applications, the number of semiconductors in series connection may be reduced drastically. This also may reduce the number of gate drivers and the number of stacked coolers and modules.
For modular multilevel converters or cascaded half-bridge topologies in high voltage applications, the number of converter cells may be reduced drastically. Again, this may reduce the number of gate drivers and the number of stacked coolers and modules. Furthermore, the volume of the entire converter may be reduced significantly.
In addition, high voltage SiC devices may provide a higher cosmic ray robustness.
Furthermore, SiC devices will allow high temperature and high-current operation and may potentially allow a significant shrinkage of SiC area and power module footprint.
Finally, modular multilevel converter and cascaded half-bridge topologies for high voltage applications based on SiC may lower the need for short circuit failure mode (SCFM) operation.
However, due to the different design and operation properties of wide bandgap semiconductor devices compared to Si devices, there may be a need for new packaging concepts for assembling these devices into modules.
For example, compared to conventional Si semiconductor devices, SiC devices have smaller chip area and may consequently have lower current ratings, which may require paralleling of an even larger number of devices.
Furthermore, high loss densities may require advanced heat spreading and cooling. In addition, very low or even negative temperature coefficients of resistance of SiC bipolar devices may demand highly uniform temperature resistances across parallel bipolar devices.
Higher operation voltages may require higher protection for partial discharges at substrate metallization edges. For example, sharp DBC (direct bonded copper substrate) Cu edges and active metal brazing protrusions with curvatures in the micrometer range may lead to considerable field crowding and are of particular concern at ultra-high voltage applications. Higher edge termination surface fields may result in a need for enhanced insulation strength and excluded contamination and moisture condensation in the vicinity of the edge termination.
Faster switching capabilities may result in higher transients and there may be a need for synchronous switching of a large multitude of parallel devices.
US 2014/0291832 A1 relates to a power semiconductor module with an IGBT and a diode interposed between two DBC (direct copper bonding) substrates and molded into a mold compound. Two cooling shells are bonded to the substrates.
EP 2 270 855 A1 relates to a double-side cooled module with two substrate plates and semiconductor components between the two substrate plates.
DE 41 03486 A1 shows a cooling arrangement with a semiconductor device mounted between two liquid cooled electrodes. The semiconductor device is arranged in an opening of an isolating plate, which is arranged between the two electrodes.